Producing light-beams



C. F. JENKINS.

PRODUCING LIGHT BEAMS.

' APPLICATION FILED APR. 16. 1918.

1,390,445., PatentedSept. 13,1921. v

Q "1 NW warren STATES PATENT oFFic CHARLES FRANCIS JENKINS, OF WASHINGTON, DISTRICT OF COLUMBIA.

PRODUGIN G LIGHT-BEAMS.

T 0 all whom it may concern Beit known that I, CHARLES FRANCIS JENKINS, a citizen of the United States, and

resident of Washington, in the District of Columbia, have invented certain new and useful Improvements in ProducingLlght- Beams, of which the following is a specification; reference being had therein to the aclost light so as to secure a much more-power-- ful beam from a given source, or to obtain a beam of a given strength while generating much less than the ordinary light, is the object of this invention.

For illustration apparatus suitable for picture projecting has been selected.

The accompanying drawing shows such apparatus in vertical section through the both because it is radiated directly from the axis of the light beam.

In this drawing, A represents an electric lamp bulb containing a light source B, pref erably of small area and with its broader faces transverse to the axis as usual in analogous apparatus. C is a plate provided with an aperture C at which pictures to be projected are exposed, and D is a common projecting lens.

Slightly in front of the source B is a tubular reflector E of approximately parabolic form adapted to reflect rays F from the source B so that they take the direction indicated at F and, exceptan outer fringe of rays, pass through the a erture C and meet at the lens D. Rays passing-rearward from the other broad face of the filament strikea reflecting coating A in the bulb and are thrown back to the center and like the rays F strike the reflector E and pass to the lens D. Rays H which fall within the angle of the dotted lines I, would naturally fail to strike the reflector E and would fail .to pass through the aperture C and would be lost. For this reason, I place at a suitable Specification of Letters Patent. Patented Sept. 13, 1921.

Application filed April 16, 1918.

Serial No. 228,891.

and the plane of the adjacent end of the re-' flector E receives only a small amount of light from the thin edge of the source B and the marginal loss at the periphery of I the lens J and at the aperture C" is very sli ht,

bviously, moving the bulb A- along the axis varies the convergence of the rays, and of course the distance at which the lens D should be placed. Indeed, the rays F may be made approximately parallel asin the case of a common parabolic reflector. In doing this, the plate C and lens D may be omitted. When this is done, the apparatus still allows radiant heat to escape freely,

bulb into the open air and because air passes through the reflector E.

The parabolic tube may be extended at its larger end without disadvantage, butat its I smaller end it must throw no rays to the lens J.

What I claim is:

The combination with a spherical electric light bulb, of an open approximately parabolic tubular reflector in position to receive rays from the bulb and focus them approximately at a distant projectinglens, a plate interposed in the light beam and provided with an exposure aperture therefor, and a lens in the axis of the beam in position to receive the rays directed centrally out of the larger end of the tubular reflector and adapted to focus them approximately at the projecting lens, said bulb being provided on the side most distant from the tubular refiector with a spherical reflecting surface.

In testimony whereof I hereunto aflix my 

